In the "B.C." comic strip, Thor often rides on a single wheel which has a rounded stone ground wheel and a wooden central axle. The sprag wheel of this invention is a practical embodiment of the Thor wheel.
Single-wheeled vehicles have been known for a long time in many different fields. The most familiar, a unicycle mounts a seat to the axle of a wheel and uses pedals for maintaining stability of the rider. Balance is achieved by the rider's being able to oscillate the wheel back and forth through the pedals.
In U.S. Pat. No. 4,241,931, an automobile tire riding vehicle is disclosed. Suitable means are placed within the inside of the tire to roll along the bead when the tire rolls. Power input means are not provided in this vehicle. A rider can only roll down a slightly sloping hill to enjoy his toy rather than being able to ride on the level.
In U.S. Pat. No. 3,306,626, a ball is adapted for riding by the person who stands on plates projecting from the ball. A plurality of one-way clutches allow skittering on the ball in one direction, while the clutches release when moved in the opposite direction. The ball reveals no means for pitch stability and results in a waddling or skittering motion when ridden rather than an imitation of the ride Thor achieves on his wheel.
Single-wheeled toys utilizing flywheels as energy storage devices are shown in U.S. Pat. Nos. 2,802,300; 3,955,429; and 3,621,607.